The bootloader is locked with a password (but you can get around it easily) and it seems to run Jungo's OpenRG firmware.

The device is not fully supported yet (but about to be)

Hardware Highlights

CPU

Ram

Flash

Network

WiFi

USB

POTS

Serial

JTag

Lantiq Danube-S XWAY@333MHz

64MiB

0.5MiB NOR + 32MiB NAND

4x ETH, ADSL2+

802.11bgn 2T2R

1x USB2.0

2xFXS, 1xFXO

Yes

EJTAG 3.1

Notes

Working:

serial :)

Ethernet (tested)

USB (tested)

NAND (tested)

TAPI/VoIP (probed ok, not tested)

ADSL (driver loads, not tested)

Not working yet:

NOR support is somehow still disturbed.

Even though JEDEC probe is enabled and added to lantiq-flash, it won't find the flash chip. From the code it already looks like some byte-swapping quirk is needed for the probe to work… Maybe something goes wrong there… Users of the BTHOMEHUBV2B reported similar problems, apparently the flash worked in 3.3.8 but stopped working with more recent kernels.

WiFi

I figured this can be done in user-space, similar to how it works on the
Netgear DGN3500B

Rebooting

The board just halts instead of rebooting.

Unsupportable:

DECT

Will probably never work (unless someone wants to implement a driver for it)

Bootloader

The bootloader is locked with a password, however, we were generously provided with a bug/feature:
If PIN 2 (next to RX) is pulled down, NAND fails. Once that happens during a normal (non-interrupted) firmware load, (i.e. while it's counting up from 0% to 100% in the boot phase) we are dropped onto an u-boot shell. Unfortunately, this U-Boot doesn't support LZMA compression (thus I'm for now testing with uncompressed uImages).

Support for a fully-featured and recent version of U-Boot is in the making.